Electric phonograph reproducer



A ril 21, 1931. J. K. JOHNSON 1,301,276

ELECTRIC PHONOGRAPH R'EPRODUCER Filed June 14, 1929 elite/0hr: 5375Patented Apr. 21, 1931 UNITED STATES PATENT OFFICE JOHN KELLY JOHNSON,OF NEW YORK, N. Y.

ELECTRIC PHONOGRAPH REPRODUCER Application filed. June 14,

. tion and which will be sensitive and eflicient form and as madeup toprovide apair of upper pole tips'7, 8, extending down through in itsoperation. j

. The various novel features of construction, combinations and relationsof parts by which the foregoing objects are attained will be understoodfrom the following specification.

The drawing accompanying and forming part of thespecificationillustrates one simple practical embodiment of the invention, but itshould be understood that the structure maybe modified as regards thisdisclosure without departure from the'true spirit and broad'sco'pe oftheinvention.

' Fig. 1 is a side elevation illustrating the position of the unit as inoperation; Fig. 2 is a broken'detail view of the device looking in thedirection of the arrow 3 inFig. 1; Fig. '3 is alongitudinal section ason substan tially the plane of line 3-3 of Fig. 2; Fig. 49' is adetailed perspective view illustrating the form of the interlockinglaminations which make up the pole pieces. j

- The device consists generally of a magnet for producingastrongmagnetic field and an armature adapted to be vibrated in thatfield and inductively associated with a suitable winding. V

The magnetic field is supplied in the present disclosure by a permanentmagnet 5 of the U or horseshoe type and a special feature of this magnetis that its ends are finishedoff on an incline of approximately 45 asindicated at 6. This structure provides areas greater thanthe-transverse cross-sectional dimensions of the magnet stock,furnishing relatively large contact surfaces for the pole pieces andalso enables the magnet to be disposed substantiallyhorizontally whilethe polar and armaturestructu're occupies a downwardly inclinedposition, indicated in Fig. 1.

The pole pieces'are shown as of laminated thecenter of the magnet coil9.and a pair of lgowerpole tips 10, 11. 1

Operating-inthe two magnetic gaps thus 1929. Serial No. 370,801.

provided is the armature 12 supported intermediate its ends by theangularly projecting stub shaft portions 13, 14, the latter being screwthreaded to receive the clamping screw 15, which secures the needle 16seated in the socket 17 provided for it in the armature.

The projecting shaft portions 13, 14 of the armature are yieldingly heldby clamp pieces 18, 19, to clamp plates 20, 21, secured by rivets 22 orthe like to opposite faces of the pole pieces. The clamp plates 20, 21are indicated as having angularly turned flanges 23 stifliening-sa-idplates, said flanges being shown as having rounded bearing seats 24therein and the clamp plates 18, 19, are shown as having V-shaped seats24, 25 opposed to said rounded bearing seats. The shaft portions of thearmature are shown as similarly shaped, that is, with rounded sides forthe rounded bearing seats and V-shaped or pointed sides, Fig. 2 to fitthe V-shaped seats in themovable clamp plates. Pads 01' cushions 27ofrubber or the like are shown as surrounding these shaft or hub portionsof the armature and the movable clamp plates are indicated as secured tothe stationary or backing plates 20, 21 by screws 28, 29, at oppositesides of the armature axis. By tightening or-loosening these clampscrews at opposite sides of the armature axis, it will be noted that thearmature may be rocked one way or the other to properly center it in themagnetic gaps.

By extending the pole tips 7 8 down through the center of the coil, themagnetic effect is increased and a more sensitive and at the same time amore powerful action is obtained. Because of the increased magnetic flowthrough the coil afforded by the polar projections extending through thecoil, the slightest vibrations of the armature are picked up andmagnified by the coil, in electrical form.

The pole pieces are suitably secured to the end faces of the magnets, inthe present disclosure, by screws 30 extending from the back of themagnet up through the inclined end faces and through the pole pieces,the nuts 31 on the upper outer ends of these screws-binding the polepieces firmly down on the inclined magnet ends.

The pole pieces are shown as of laminated form and to allow for thepeculiar polar arrangement disclosed, the laminations are illustrated inFig. 4 as made up in four different shapes, a long length 32 equal tothe full length of the pole piece, a shorter length 33 cut ofi at theupper end, a wide-section 34 equal to the full width of the pole pieceand a narrower section 35. The pieces 32 and 35 are complemental to eachother to form the upper and lower pole extensions 7 and 10 and insimilar fashion, the shorter and wide sections 33, 34 are complementaryto complete the pole projections, it being noted that the wide section34 overlaps the break be tween the long and the narrower sections 32, 35and that the long section 32 overlaps the break between the wide section34 and the shorter section 33. In assembling the L-shaped sections 34,35 are arranged alternately, a narrow and a wide section, the outer polepieces 32, 33 are overlaid in alternations and the two sets areinterleaved after first passing the polar projections of the inner setsdown through the coil- After assembling in this fashion, the two polepieces may be bound together by the clamp or bridge pieces 20, 21 and bythe extra. securing bar 36 at the top, rivets 37 or other suitablefastenings being employed for securing this additional clamp bar. Thepole pieces can thus be assembled with the coil and then fastened up asa complete single unit ready to go on the magnet as such, only the twoscrews and nuts being required for properly fastening the unit to themagnet.

The gain in area attained by facing off the ends of the magnet oninclines permits the piercing of these magnet ends for the bolts 30without losing too much contact area be tween the pole'pieces and magnetends. The armature is a relatively short, straight, light piece of metaland therefore particularly efficient for its purpose. The magnet endsmay be pierced before the magnet is hardened and theonly machining thenrequired, is the grinding or facing of the inclined ends of the magnet.The spool of the coil isheld inplace by the polar projections 7 8,extending therethrough, the L-shaped form of the magnet laminationsproviding the necessary space at the sides of these projections toreceive the body'of the spool and the coil carried thereby. -Thestructure is particularly simple and such as can be readily manufacturedand assembled at a 10W cost of-production.

The bridging or connecting strips or plates 36, 20, 21 and clamp plates18, 19, may be of brass or any other suitable non-magnetic material, soas not to short circuit the magnetic flux across the pole tips, 7 8 and10, 11.

WVhat is claimed is:

1. An electrical phonograph pickup unit, comprising a U-type magnethaving its ends angled ofi at an incline to the general plane of themagnet, pole pieces secured in contacting engagement over the slantingsurfaces of said angled magnet ends, a coil supported by said polarstructure and an armature supported by the polar structure in vibratingrelation to the pole pieces and the coil.

2. An electrical phonograph pickup unit, comprising a U-type magnethaving its ends angled off at an incline to the general plane of themagnet, pole pieces secured in contacting engagement over the slantingsurfaces of .said angled magnet ends, a coil supported by said polarstructure, an armature supported by the polar structure in vibratingrelation to the pole pieces and the coil, said angled ends of the magnetbeing pierced substantially at right. angles to said inclined surfacesand securing bolts for the pole pieces extending through said piercedmagnet ends.

3. An electrical phonograph pickup unit, comprising a U-type magnethaving its ends angled off at an incline to the general plane of themagnet, pole pieces secured in contact ing engagement over the slantingsurfaces of said angled magnet ends, a coil supported by said polarstructure, and an armature supported by the polar structure in vibratingrelation to the pole pieces and the coil, said pole pieces having polarprojections extending throughthe coil.

4. An electrical phonograph pickup unit, comprising a magnet, a pickupcoil, spaced opposed pole pieces carried by the magnet and having polarprojections both extending through said pickup coil and a vibratingarmature operatively associated with said polar projections. I

5. An electrical phonograph pickup unit, comprising a magnet, a pickupcoil, spaced opposed pole pieces carried by the magnet and having polarprojections both extending through said pickup coil and a vibratingarmature operatively associated with said polar projections, said polepieces consisting of generally L-shaped polar laminations arranged inoverlapping order with the legs of certain of said L-shaped laminationsprojecting through said pickup coil. V

6. In a device of the character disclosed. polar laminations ofgenerally L-shaped form and of different dimensions, said laminationsbeing, arranged in over-lapping order to break oints between thelaminations, and said laminations in the assembled relationdescribedhaving opposed polar projections, an open center coil"surrounding said polar projections and a vibrating armature supported tooperate between said projections.

7. In apparatus of the character disclosed, a bipolar magnetsupported'in a generally horizontal position and having its endsfinished on a downwar'd and forward slant, downwardly and forwardlyinclined pole piecessecured in flatengagement over said downwardly andforwardly inclined magnet ends, an armature mounted for oscillation inrespect to said pole pieces and a winding inductively associated withsaid armature.

8. In a device of the character disclosed,

a magnet, an open coil, pole pieces carried by said magnet and havingpole tips projecting through said coil and an armature mounted incooperative relation to said pole tips.

m 9. In a device of the character disclosed, a magnet, pole piecescarried thereby and provided with two pairs of opposed pole tipsarranged in spaced relation, an armature pivoted intermediate its endsand having its opposite ends positioned in cooperative relation to thetwo pairs of opposed pole tips and a coil surrounding one pair of saidpole tips.

10. In a device of the character disclosed, a magnet, pole piecescarried by said magnet,

said pole pieces having an upper pair of polar projections and a lowerpair of polar projections, the upper pair of polar projections beingelongatedan'd having clear space about the same, a coil surrounding saidupper polar projections and located in the space surrounding the sameand an armature in cooperative relation with both the sets of polarprojections and supported intermediate its ends in the space between thetwo sets of polar projections.

11. In a device of the character disclosed, a bipolar magnet having itsends finished on an incline, pole pieces secured in fiat engagement oversaid inclined en'd surfaces of said magnet and thereby positioned ininclined relation to the body of the magnet, a movable element supportedby said pole pieces in inclined relation to the body of the magnet and apower transmission member connected with 40 said movable element ininclined relation to the body of the magnet.

12. In a device of the character disclosed, a bipolar magnet,cooperating pole pieces attached to the poles of said magnet, said polepieces having separated generally parallel polar projections withclearance space about the same, an open center coil surrounding saidpolar projections and occupying the clearance space about the same and amovable element disposed in cooperative relation to said polarprojections.

In testimony whereof I afiix my signature.

J. KELLY JOHNSON.

